The prevalence of obesity is rapidly increasing and has reached epidemic proportions in the United States. This increase is of grave concern because obesity is associated with the development of several chronic diseases including cardiovascular disease, diabetes, some forms of cancer, and joint disorders. In recent studies, it has been demonstrated that physical exercise has a pronounced protective effect against weight gain. This study proposes to further those investigations by measuring the effects of recent prior moderate intensity exercise on the partitioning of recently ingested fats between oxidation and storage. This will be accomplished using stable isotope techniques and 24 hour respiratory gas analysis. Any increase in the partitioning of dietary fat to oxidation will be protective against fat deposition and weight gain. The long-term goals of the project are to improve the recommendations for the prevention and treatment of obesity.